Optical member and method of manufacturing the same

ABSTRACT

An optical member including an oxide layer that has a stable fine textured structure and is excellent in durability is provided. The optical member includes a base material and an antireflection coating on a surface of the base material. The antireflection coating includes at least an oxide layer having a fine textured structure on the surface, and the oxide layer contains a phosphate compound. Furthermore, a method of manufacturing the optical member is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical member and a method ofmanufacturing the same. More specifically, the present invention relatesto an optical member having a fine textured structure of an oxide on thesurface and a method of manufacturing the same.

2. Description of the Related Art

For example, eyeglass lenses, optical lenses, solar panels, cathode-raytubes, filters, and display panels are required to be low in lightscattering and reflection of the surfaces thereof. As a method ofachieving this requirement, a single- or multi-layer antireflectioncoating that is controlled in the refractive index and thickness isused. Such a case is known that the antireflection properties of thecoating change depending on the wavelength and the angle of incidenceand that the realization of high-performance antireflection propertiesin broad ranges of the wavelength and the angle of incidence isdifficult.

In addition, it is known that fine textured formed on the surface ofglass can impart an antireflection function to the glass. In particular,an antireflection function over a broad range of the angle of incidencecan be expected if the texture is smaller than the wavelength. Asmethods for fining, chemical etching or mechanical processing of glasssurfaces is proposed. In the chemical etching and the mechanicalprocessing, a fineness smaller than the wavelength of visible light isdifficult. Thus, chemical etching or mechanical processing that canrealize antireflection properties for an application requiringtransparency in wavelength of visible light has not been developed.Furthermore, a coating film forming a textured structure on a glasssurface has been investigated. For example, in Japanese PatentPublication No. 61-48124, it is disclosed that an antireflection coatingformed on a transparent material such as glass by converting a metalfilm of aluminum, magnesium, zinc, or an alloy thereof into an oxide ora hydroxide and that the antireflection coating constitutes discreteleaflets having various heights and shapes. Japanese Patent Laid-OpenNo. 9-202649 discloses a transparent alumina film that is randomlyagglomerated like a petal. The film is formed by applying a coatingsolution containing at least an aluminum alkoxide and a stabilizer ontoa substrate to form an amorphous alumina film, treating the filmhydrothermally, and drying it.

Many coating films as shown in Japanese Patent Publication No. 9-202649are generally porous. In general, glasses having a high refractive indexused as base materials contain oxide components such as an alkali oxide,an alkaline earth oxide, or boric oxide that are low in resistance towater and humidity. If these glasses are used as a base material forcoating, water or humidity in the air penetrates to the surface of thebase material, and an alkali oxide, an alkaline earth oxide, or boricoxide contained in the base material is released to cause fogging orwhitening of the surface or the interface thereof. In addition, in thecase of porous oxides, especially their unstable components such as awater-soluble component and a component that is dissolved andredeposited in water undergo a hydration reaction when the base materialhaving a surface layer of porous oxides is brought into contact withmoisture. Thereby, optical characteristics are deteriorated with thelapse of time. Furthermore, dissolution or corrosion of such asdecomposition caused by the porous oxide itself may occur under anatmosphere containing an acid.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the aforementionedcircumstances and provides an optical member including an oxide layerthat has a stable fine textured structure on the surface and isexcellent in durability due to the stabilized fine textured structure.The present invention further provides a method of manufacturing such anoptical member.

The optical member according to the present invention includes a basematerial and an antireflection coating on a surface of the basematerial. The antireflection coating includes at least an oxide layerthat has a fine textured structure on the surface and contains aphosphate compound.

The method of manufacturing the optical member according to the presentinvention is of manufacturing an optical member having a base materialand an oxide layer. The method includes forming an oxide layer on asurface of a base material, forming a fine textured structure on thesurface of the oxide layer, and bringing a water-soluble phosphoric acidcompound into contact with the oxide layer provided with the finetextured structure on the surface.

According to the present invention, a base material is provided with anoxide layer having a fine textured structure on the surface and, inaddition, stability of the fine textured structure of the oxide layer isremarkably improved by impregnating the oxide layer with a phosphatecompound. The present invention can be applied to an optical glasscontaining an alkali, an alkaline earth, or boron overcoming adisadvantage in durability from the glass. Thus, an optical memberhaving broad optical characteristics can be provided.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an optical member according to a first embodimentof the present invention.

FIG. 2 is a diagram of an optical member according to a secondembodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS First Embodiment

FIG. 1 shows an optical member according to a first embodiment of thepresent invention. The embodiment will be described below.

The optical member according to the first embodiment includes a basematerial 11 such as glass and an oxide layer 12 such as composite ofaluminum oxide and aluminum hydroxide oxide disposed on the opticalmember. The oxide layer 12 has a fine textured structure on the surfaceand a phosphate compound-containing layer 13.

A fine textured structure of the present invention may be unevenness ofthe micron order or the submicron order. The fine textured structure maybe a three-dimensional structure formed by solid and gaps there among.Oxide for solid may be in a crystalline state, an amorphous state, or acombination of the crystalline and amorphous states. The fine texturedstructure has a shape that can sequentially decrease refractive indicestoward the surface of the oxide layer (“the surface of the oxide layer”is the surface of the optical member and the interface with the air).Accordingly, hazing and antireflection functions can be imparted to thesurface of the optical member by controlling reflection properties andtransmission functions of the surface by the fine textured structure.When the fine textured structure of the oxide layer has regularity,reflection and transmission functions are exhibited at a specific angleor a specific wavelength. In order to realize the antireflectionfunction, the fine textured structure of the surface is preferablyconstituted by anisotropic crystalline fine particles of an oxide. Theshape of the anisotropic crystalline fine particles of an oxide may be,for example, plate- or needle-like. Examples of the anisotropiccrystalline fine particles of an oxide include particles of oxides suchas magnesium oxide, zinc oxide, titanium oxide, and aluminum oxide;hydroxides such as boehmite (aluminum hydroxide oxide); and complexoxides such as lithium silicate and titanium silicate. Among them,plate-like particles readily form a spatially graded structure in thedirection vertical to the face and are hence particularly preferred.Specifically, plate-like boehmite particles prepared by a hydrothermalreaction is preferably used. The wavelength range of light in which anantireflection function can be realized, depends on the size ofcrystalline fine particles of an oxide (the height of the texture) andthe size of texture in the face direction. In an antireflection coatingcorresponding to visible light, the height of texture is preferably inthe range of 0.1 to 5 μm. With a height of 0.1 μm or more, anantireflection function in the visible light range can be realized.Furthermore, with a texture height of 5 μm or less, the texturedstructure can maintain a high mechanical strength. The phosphatecompound imparts stability to the oxide of the fine textured structure.The phosphate compound may cover at least the surface of the oxideparticles and may lie in the fine textured structure.

If the phosphate compound is not present, water and humidity in the airpenetrates to the surface of the base material because the oxide layeris porous. As a result, an alkali oxide, an alkaline earth oxide, orboric oxide contained in the base material is released to cause foggingof the surface or the interface thereof. In addition, some reactions mayprogress in the oxide layer to cause a change in the properties such asrefractive index, etc. The phosphate compound of the present inventionsuppresses the reactivity of the unstable oxide such as amorphousoxides. With this, the change of the oxide caused by moisture in the airis inhibited. Accordingly, the release and the degradation of the oxideand disruption of the textured structure caused thereby do not occureven under an acidic atmosphere. The acid resistance and durability ofthe textured structure are further improved and the opticalcharacteristics are further stabilized by also covering the surfaces ofthe anisotropic crystalline fine particles of an oxide constituting thetextured structure with the phosphate compound.

Any phosphate compound can be used in the present invention withoutspecific limitation as long as it is insoluble in water. Examples of thephosphate compound include magnesium phosphate, calcium phosphate, zincphosphate, barium phosphate, aluminum phosphate, gallium phosphate,lanthanum phosphate, titanium phosphate, and zirconium phosphate. Whenthe base material used in the optical member has a low durability, adense region is preferably formed in the oxide layer by the phosphatecompound.

Examples of the base material of the optical member according to thepresent invention include glasses, plastics. Typical examples of theplastic base material include films and products of thermoplastic resinssuch as polyester, triacetyl cellulose, cellulose acetate, polyethyleneterephthalate, polypropylene, polystyrene, polycarbonate,polymethylmethacrylate, ABS resins, polyphenylene oxide, polyurethane,polyethylene, and polyvinyl chloride; and cross-linked films andcross-linked products of thermosetting resins such as unsaturatedpolyester resins, phenolic resins, cross-linked polyurethane,cross-linked acrylic resins, and cross-linked saturated polyesterresins.

When an optical glass containing an alkali, an alkaline earth, or boronis used as the base material, an oxide layer having a fine texturedstructure on the surface is formed on the optical glass. The oxide layerfunctions as an antireflection coating having a high antireflectionfunction. Since many glasses having a refractive index of 1.4 to 1.9 canbe proposals, an optical lens having high-performance antireflectionfunction in a broad range can be realized. The oxide layer having thefine textured structure containing the phosphate compound according tothe present invention prevents the degradation caused by a componenthaving a low water resistance. Typical examples of the optical glassbase material include barium flint, barium crown, borate crown,lanthanum flint, and lanthanum crown glasses.

Second Embodiment

FIG. 2 shows an optical member according to a second embodiment of thepresent invention. The embodiment will be described below.

In this embodiment, only aspects that are different from the firstembodiment will be primarily described.

The optical member according to the second embodiment includes a basematerial 21 such as glass and an oxide layer 24 such as aluminumhydroxide oxide. The oxide layer 24 is disposed on a surface of theoptical member and has a fine textured structure on the surface. Theoxide layer 24 further includes phosphate compound-containing layers 25.Furthermore, the oxide layer 24 includes an amorphous oxide layer 23such as aluminum oxide having a thickness of 1 nm or more. The term“amorphous” in this embodiment means that diffraction due tocrystallization is not observed by X-ray scattering or neutronscattering method and may be observed as a continuous film or anaggregation of particles with a particle diameter of 50 nm or less by ageneral observation method.

The phosphate compound covers at least the surfaces of the oxideparticles and forms the phosphate compound-containing layer 23. As willbe described blow, when a phosphoric acid compound penetrates gaps ofthe fine textured structure of the surface of the oxide layer 24, italso reacts with the amorphous oxide layer 23 to form a layer 25 of aphosphate compound on the surface of the amorphous oxide layer. A denselayer is formed by that the phosphate compound lies in the amorphouslayer too. Even if the reaction with the phosphoric acid compoundspreads over the entire amorphous oxide layer to change the entireamorphous oxide layer 23 into the phosphate compound-containing layer25, the effect of the present invention can be achieved. Furthermore,the phosphate compound may lie in the fine textured structure. Inaddition, if necessary, an intermediate layer 22 having a refractiveindex different from that of the base material may be previouslydisposed on the surface of the base material, in order to improve theantireflection function. The intermediate layer may be formed by a knownmethod such as vapor deposition or a sol-gel method. Examples of theintermediate layer include films of silica, titanium oxide, tin oxide,aluminum oxide, yttrium oxide, tantrum oxide, and complex films thereof.When there are relationships, n_(b)≧n_(s)≧n_(a), among the refractiveindex n_(b) of the base material, the refractive index n_(s) of theintermediate layer, and the refractive index n_(a) of the amorphouslayer, the function is more effective. By controlling the refractiveindices as above, the refractive indices can be gradually decreased fromthe base material to the amorphous oxide layer. In addition, the finetextured structure can sequentially decrease refractive indices from theamorphous layer toward the surface of the oxide layer, and thereby theantireflection effect can be significantly enhanced.

A method of manufacturing the optical member according to the presentinvention will now be described. The method of the present inventionincludes a process forming an oxide layer on a surface of a basematerial, a process forming a fine textured structure on the surface ofthe oxide layer, and a process bringing a water-soluble phosphoric acidcompound into contact with the oxide layer provided with the finetextured structure on the surface.

In this embodiment, a precursor film that becomes the oxide layer isformed on a surface of the base material. Then, a fine texturedstructure is formed to the precursor film. The fine textured structuremay be formed by any method without any limitation and can be formed by,for example, phase separation, oxidation, phase transition,crystallization, or selective elution of the precursor film. Preferably,anisotropic crystalline particles of an oxide are formed by bringing ametal film or a metal oxide film into contact with water.

In a case of a metal film, the metal film is oxidized by the contactwith water to form crystalline particles of an oxide or hydroxide forforming the fine textured structure. Examples of the metal includealuminum, magnesium, and zinc. Aluminum is preferred. By using aluminum,plate-like crystalline boehmite particles having a size of severalhundreds nanometers or less are formed. The metal film can be preferablyformed by vapor deposition, ion plating, or sputtering.

The metal oxide film may be formed by, for example, sol-gel method,sputtering, or vapor deposition. The metal oxide film is crystallized orpartially selectively etched by the contact with water to form the finetextured structure. The oxide film is preferably amorphous and is elutedand reprecipitated by the contact with water to form the fine texturedstructure of the crystalline fine particles. Examples of the oxideinclude aluminum oxide, titanium oxide, and zinc oxide. Furthermore,according to need, the oxide film may be a complex film containing suchan oxide as a main component, and other oxide components such as silica,etc. which are not grown to particles alone, as solid-solutioncomponents of the particles or grain boundary components. An amorphousoxide containing aluminum oxide as a main component is preferably usedas the metal oxide film forming the antireflection coating on thesurface. The amorphous aluminum oxide film is converted into a finetextured structure with the growth of particles. It is preferable thatan amorphous precursor film (amorphous layer) remains so as to have athickness of 1 nm or more. As described above, since the fine texturedstructure can sequentially decrease refractive indices from the boundarywith the amorphous layer toward the surface of the oxide layer, a hazingfunction and an antireflection function can be imparted to the surfaceof the optical member by controlling reflection properties andtransmission functions of the surface of the optical member by the finetextured structure. Since the amorphous layer remains, the phosphoricacid compound reacts with the amorphous layer too to form a dense layercontaining the phosphate compound and being excellent in waterresistance and acid resistance.

The process of the contact with water is basically conducted underconditions suitable for the growth of particles and preferably at 50° C.or more and more preferably at 60° C. or more. The period of time forthe contact process is not specifically limited and is preferably fiveminutes or more and three hours or less.

In the surface treatment process for bringing the obtained oxide layerprovided with the fine textured structure on the surface into contactwith a water-soluble phosphoric acid compound, the water-solublephosphoric acid compound reacts at least with a part of the oxide toform a phosphate compound in the oxide layer.

Any compound having a phosphate group and being water-soluble can bebasically used as the water-soluble phosphoric acid compound of thepresent invention. Examples of the phosphoric acid compound includephosphoric acid, polyphosphoric acid, amine phosphate, aminepolyphosphate, metal dihydrogen phosphate, and metal hydrogen phosphate.These phosphoric acid compounds can be used alone or as a combination oftwo or more thereof. When the reactivity between the phosphoric acidcompound and the oxide layer having the fine textured structure is high,the reaction with the oxide component of the fine textured structure mayoccur rapidly to deteriorate the fine textured structure. Accordingly,the reactivity is controlled not to damage the antireflection functionof the fine texture, and metal dihydrogen phosphate or amine phosphateis preferably used. Examples of the metal dihydrogen phosphate includecalcium dihydrogen phosphate, aluminum dihydrogen phosphate, zincdihydrogen phosphate, and titanium dihydrogen phosphate. Examples of theamine phosphate include ammonium dihydrogen phosphate, diammoniumhydrogen phosphate, triammonium phosphate, methylamine phosphate,ethylamine phosphate, and alkanolamine phosphate. The phosphoric acidcompound reacts with the oxide layer having the fine textured structureto form a water-insoluble metal phosphate layer on the surface of theoxide component having the fine textured structure.

The water-soluble phosphoric acid compound is preferably used as anaqueous dispersion or a dispersion in a water-soluble organic solventsuch as alcohol, and an aqueous dispersion is more preferred. Thecontent of the water-soluble phosphoric acid compound is preferably0.01% (by weight) or more and 30% (by weight) or less and morepreferably 0.05% or more and 20% or less. The effect of the phosphoricacid compound in the oxide layer having the fine textured structureappears when the content is 0.01% or more. In addition, the finetextured structure is maintained and also the optical characteristicsdue to the fine textured structure are not damaged when the content is30% or less.

The contact of the water-soluble phosphoric acid compound is conductedby immersing a base material provided with the oxide layer having thefine textured structure into a dispersion of the water-solublephosphoric acid compound or a coating method such as dipping, spinning,or spraying. Furthermore, when an excessive amount of the phosphoricacid compound is applied to the oxide layer having the fine texturedstructure, a process for washing or rinsing out the excessive phosphoricacid compound with a dispersion solvent such as water or alcohol may beconducted.

More specifically, when the fine textured structure is a layer ofanisotropic oxide particles, the phosphoric acid compound reacts withthe anisotropic oxide particles to form a film of a water-insolublephosphate compound on the particle surfaces. In a region where particleshaving a particle diameter of 100 nm or less are present at a highparticle density, a dense phosphate compound region is formed.Furthermore, when the amorphous layer is present in the oxide layer, thephosphoric acid compound reacts with the amorphous layer too to form adense layer containing a phosphate compound and being excellent in waterresistance. In such a case, even if an optical glass containing anelement selected from the group consisting of an alkali, an alkalineearth, and boron, which are low in water resistance, is used as a basematerial, the penetration of moisture into the glass is inhibited.Consequently, the optical member exhibiting excellent durability under ahigh temperature and high humidity environment can be obtained.

When it is necessary to enhance the reaction between the phosphoric acidcompound and the oxide component having the fine textured structure, aprocess for drying at 300° C. or less may be conducted after bringingthe phosphoric acid compound into contact with the oxide component.

EXAMPLES

The present invention will now be more specifically described withreference to Examples, but is not limited thereto.

Fine textured structures prepared in the following Examples andComparative Examples were evaluated by the following methods. Thecross-sections of samples were observed with a field emission scanningelectron microscope (FE-SEM, Hitachi S4500) for evaluating the finetextured structures. Haze values, which are generally used as a valuefor indicating the degree of fogging, were measured using a haze meter(Nippon Denshoku, NDH2000) in order to evaluate the degree of fogging.

For stability of the fine textured structure, the samples were exposedto a temperature of 60° C. and a relative humidity of 90% using acirculator for the high temperature and the high humidity for continuous1000 hours and then evaluated for the cross-sections and the degree offogging, again. For acid resistance, samples were immersed in a 0.01 Nhydrochloric acid aqueous solution, and then observed of any changes intheir appearance.

Example 1

A coating solution for a sol-gel method was prepared.Aluminum-sec-butoxide [Al(O-sec-Bu)₃] was dissolved in 2-propanol (IPA)with stirring, and ethyl acetoacetate (Eacac) was added thereto as astabilizer for the coating solution at a molar ratio ofAl(O-sec-Bu)₃:IPA:Eacac=1:20:1. The resulting mixture was stirred for 30minutes, and 0.01 N hydrochloric acid was added thereto as the source ofH₂O for the hydrolysis and a catalyst with a molar ratio ofH₂O:Al(O-sec-Bu)₃=1:1. The obtained mixture was subjected to a reactionfor 48 hours to give a coating solution of an amorphous aluminum oxide.

A phosphoric acid compound treatment solution was prepared. One part byweight of aluminum dihydrogen phosphate [Al(H₂PO₄)₃] was dissolved in200 parts by weight of pure water, and the resulting solution was leftto stand for about two days. The solution was filtered through a filterof 0.1 μm to give a transparent solution. This solution was used asphosphoric acid compound treatment solution 1.

Three silica glass substrates having a thickness of 1 mm were coatedwith the coating solution by a dipping method by immersing thesubstrates in the coating solution and lifting them at a speed of 3mm/sec under a relative humidity of 50%. Then, the substrates were driedin the air for 30 minutes and subsequently heat-treated at 300° C. for 1hour. The above procedure was repeated to conduct the coating twice togive silica glasses each provided with an amorphous aluminum oxidelayer. The obtained silica glasses were treated with hot water to formfine textured of aluminum oxide. Each silica glass was put in astainless steel holder and was immersed in pure water at 80° C. for 30minutes and then dried at 100° C. Two of the three substrates wereimmersed in the phosphoric acid compound treatment solution 1 and thenlifted at a speed of 3 mm/sec. The substrates were heated at 60° C. for1 hour to give silica glasses having an oxide layer provided with thefine textured structure. One of the two silica glasses was stored in avacuum desiccator, and the other silica glass was subjected to adurability test under the above-mentioned durability test conditions (atemperature of 60° C., a relative humidity of 90%).

The sample subjected to the durability and the sample stored in thevacuum desiccator were evaluated using a spectrophotometer. It wasconfirmed that both samples had a transmittance of 99.6% at 500 nm andno change in appearance occurred. Furthermore, the surfaces of bothsamples were observed for the fine textured structure, and it wasconfirmed that each sample had an amorphous layer with a thickness of 70nm and a layer of a textured structure composed of plate-like particleswith a thickness of about 350 nm on the surface. The sample was notchanged under high temperature and humidity conditions compared to thesample stored in the vacuum desiccator. For acid resistance evaluation,this sample was immersed in a 0.01 N hydrochloric acid aqueous solutionfor 15 minutes and then rinsed with distilled water and dried at 80° C.The sample was confirmed that no changes in the appearance and in thetransmittance were caused by the immersion in hydrochloric acid.

Comparative Example 1

The sample that was not coated with aluminum dihydrogen phosphate inExample 1 was subjected to the durability test as in Example 1. Theappearance was similar to that of the sample stored in vacuum in Example1, but the observation of the cross section with an electron microscopeconfirmed that the amorphous layer had a thickness of 50 nm. Thus, thesample was unstable and the reaction of the amorphous layer occurredunder a high temperature and high humidity condition, different from thesample coated with aluminum dihydrogen phosphate. This sample wasfurther immersed in a 0.01 N hydrochloric acid aqueous solution as inExample 1 and then evaluated for acid resistance. It was found that thealuminum oxide film on the surface completely disappeared. Thus, thesample not coated with aluminum dihydrogen phosphate did not have acidresistance.

Example 2

Two soda-lime-silica glasses (Na₂O: 17 wt %) having a thickness of 1 mmwere coated with the amorphous aluminum oxide coating solution ofExample 1 by a dipping method at a lifting speed of 3 mm/sec under arelative humidity of 50%. Then, the glasses were dried in the air for 30minutes and subsequently heat-treated at 300° C. for 1 hour. The aboveprocedure was repeated to conduct the coating twice to give glasssubstrates each provided with an amorphous aluminum oxide layer. Theobtained glass substrates were treated with hot water to form a finetexture of aluminum oxide. Each glass substrate was put in a stainlesssteel holder and was immersed in pure water at 80° C. for 30 minutes andthen dried at 100° C. One of the two glass substrates was immersed inthe phosphoric acid compound treatment solution 1 and then lifted at aspeed of 3 mm/sec. The glass substrate was heated at 60° C. for 1 hourto give glass 2.

The glass 2 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%), and it was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 99.7%, and the haze value measured with a hazemeter (Nippon Denshoku, NDH2000) was 0.12. These values were not changedcompared with those before the durability test. Furthermore, the crosssection of the sample was observed with an electron microscope, and itwas found that the sample had an amorphous layer with a thickness of 30nm and a layer having a textured structure composed of plate-likeparticles with a thickness of about 320 nm. It was also confirmed thatthese measurement values were not different from those before thedurability test.

Comparative Example 2

The glass provided with a fine textured structure but not coated withaluminum dihydrogen phosphate in Example 2 and an untreatedsoda-lime-silica glass were subjected to the durability test. Bothglasses had cloudiness. The haze values of the above glasses measuredwith a haze meter were 2 and 2.5, respectively.

Example 3

A phosphoric acid compound treatment solution was prepared. One part byweight of ammonium phosphate [(NH₄)₃PO₄] was dissolved in 200 parts byweight of pure water, and the resulting solution was left to stand forabout two days. The obtained transparent solution was used as phosphoricacid compound treatment solution 2.

Two optical glasses containing 11% of Na₂O and having a refractive indexof 1.81 were used as the base material and provided with a vapordeposition film of aluminum using a tungsten heater in a vacuum. Theobtained glass substrates were each put into a stainless steel holderand immersed in boiling water for 1 hour and then heated at 100° C. for1 hour. One of two glass substrates was immersed in the phosphoric acidcompound treatment solution 2 and then lifted at a speed of 3 mm/sec.The glass substrate was heated at 60° C. for 1 hour to give glass 3.

The glass 3 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%). It was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 98.4%, and the haze value measured with a hazemeter was 0.11, which were similar to those before the durability test.Furthermore, the cross section of the sample was observed with anelectron microscope, it was found that the sample had a layer having atextured structure composed of plate-like particles with a thickness ofabout 155 nm. These measurement values were found to be similar to thosebefore the durability test.

Comparative Example 3

The glass substrate that was not treated with ammonium phosphate inExample 3 was subjected to the durability test. It was found that theglass substrate became opaque and that the haze value measured with ahaze meter increased to 1.2.

Example 4

Two optical borosilicate glasses (Na₂O: 9 wt %, K₂O: 9 wt %) having athickness of 1 mm and refractive index of 1.58 were coated with theamorphous aluminum oxide coating solution of Example 1 by a dippingmethod at a lifting speed of 3 mm/sec under a relative humidity of 50%.Then, the glasses were dried in the air for 30 minutes and subsequentlyheat-treated at 300° C. for 1 hour. The above procedure was repeated toconduct the coating twice to give glass substrates each provided with anamorphous aluminum oxide layer. The obtained glass substrates weretreated with hot water to form a fine texture of aluminum oxide. Eachglass substrate was put in a stainless steel holder and was immersed inpure water at 80° C. for 30 minutes and then dried at 100° C. One of twoglass substrates was immersed in the phosphoric acid compound treatmentsolution 1 and then lifted at a speed of 3 mm/sec. The glass substratewas heated at 60° C. for 1 hour to give glass 4.

The glass 4 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%). It was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 99.6%, and the haze value measured with a hazemeter was 0.09, and these values were similar to those before thedurability test. Furthermore, the cross section of the sample wasobserved with an electron microscope, it was found that the sample hadan amorphous layer with a thickness of 27 nm and a layer having atextured structure composed of plate-like particles with a thickness ofabout 370 nm. Thus, it was confirmed that these measurement values weresimilar to those before the durability test.

Example 5

A phosphoric acid compound treatment solution was prepared. One part byweight of calcium dihydrogen phosphate [Ca(H₂PO₄)₂H₂O] was dissolved in100 parts by weight of pure water, and the resulting solution was leftto stand for about two days. The obtained transparent solution was usedas phosphoric acid compound treatment solution 3.

A soda-lime-silica glass (Na₂O: 17 wt %) having a thickness of 1 mm wascoated with the amorphous aluminum oxide coating solution of Example 1by a dipping method at a lifting speed of 3 mm/sec under a relativehumidity of 50%. Then, the glass was dried in the air for 30 minutes andsubsequently heat-treated at 300° C. for 1 hour. The above procedure wasrepeated to conduct the coating twice to give a glass substrate providedwith an amorphous aluminum oxide layer. The obtained glass substrate wastreated with hot water to form a fine texture of aluminum oxide. Theglass substrate was put in a stainless steel holder and was immersed inpure water at 80° C. for 30 minutes and then dried at 100° C. The glasssubstrate was immersed in the phosphoric acid compound treatmentsolution 3 and then lifted at a speed of 3 mm/sec. The glass substratewas heated at 60° C. for 1 hour to give glass 5.

The glass 5 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%), and was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 98.2%, and the haze value measured with a hazemeter was 0.10. Furthermore, the cross section of the sample wasobserved with an electron microscope, and it was found that the samplehad an amorphous layer with a thickness of 15 nm and a layer having atextured structure composed of plate-like particles with a thickness ofabout 390 nm. This phosphoric acid compound treatment compound containscalcium, which is an alkaline earth metal. However, the conformation isdifferent from that of alkaline earth metals contained in a basematerial. When a substrate having an aluminum oxide layer is immersed inthe phosphoric acid compound treatment solution, the phosphoric acidcompound reacts with the aluminum oxide component to form awater-insoluble composite layer containing calcium phosphate andaluminum phosphate. This layer prevents moisture from penetrating intothe glass base material. In addition, since calcium itself is tightlybound in a form of a salt of phosphoric acid, a change in opticalproperties, which is caused by migration of calcium atoms in thealuminum oxide layer, does not occur.

Example 6

A 0.5% zinc dihydrogen phosphate [Zn(H₂PO₄)₂] aqueous solution(treatment solution 4) was used as the phosphoric acid compoundtreatment solution. The 0.5% zinc dihydrogen phosphate [Zn(H₂PO₄)₂]aqueous solution (treatment solution 4) was prepared. One part by weightof zinc dihydrogen phosphate [Zn(H₂PO₄)₂] was dissolved in 200 parts byweight of pure water.

A soda-lime-silica glass (Na₂O: 17 wt %) having a thickness of 1 mm wascoated with the amorphous aluminum oxide coating solution of Example 1by a dipping method at a lifting speed of 3 mm/sec under a relativehumidity of 50%. Then, the glass was dried in the air for 30 minutes andsubsequently heat-treated at 300° C. for 1 hour. The above procedure wasrepeated to conduct the coating twice to give a glass substrate providedwith an amorphous aluminum oxide layer. The obtained glass substrate wastreated with hot water to form a fine texture of aluminum oxide. Theglass substrate was put in a stainless steel holder and was immersed inpure water at 80° C. for 30 minutes and then dried at 100° C. The glasssubstrate was immersed in the phosphoric acid compound treatmentsolution 4 and then lifted at a speed of 3 mm/sec. The glass substratewas heated at 60° C. for 1 hour to give glass 6.

The glass 6 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%), and was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 98.5%, and the haze value measured with a hazemeter was 0.11. Furthermore, the cross section of the sample wasobserved with an electron microscope, it was found that the sample hadan amorphous layer with a thickness of 35 nm and a layer having atextured structure composed of plate-like particles with a thickness ofabout 400 nm.

Example 7

An optical glass having a thickness of 1 mm, containing 11 wt % Na₂O,and having a refractive index of 1.81 was used as the base material.

Tetraethoxysilane (TEOS) was dissolved in ethanol (EtOH), and a 0.01 MHCl aqueous solution was added thereto as a catalyst at a molar ratio ofTEOS:EtOH:HCl (aq)=1:40:2. The resulting mixture was stirred for sixhours. Separately, titanium n-butoxide (TBOT) was dissolved in ethanol,and ethyl acetoacetate was added thereto as a stabilizing component at amolar ratio of TBOT:EtOH:EAcAc=1:20:1. The resulting mixture was stirredat room temperature for three hours. This TiO₂ sol solution was added tothe above SiO₂ sol solution at a molar ratio of SiO₂:TiO₂=70:30. Theresulting mixture was stirred at room temperature for 2 hours to give acoating solution for a SiO₂—TiO₂ intermediate film.

A coating film was formed on a surface of the glass substrate by adipping method by immersing the glass substrate in the coating solutionfor an intermediate film and lifting it at a speed of 2 mm/sec under arelative humidity of 50%. After drying, the glass substrate washeat-treated at 300° C. for 1 hour, and a glass substrate coated with atransparent amorphous intermediate oxide film including titanium andsilicon was obtained.

The glass substrate provided with the intermediate film was coated withan amorphous aluminum oxide coating solution of Example 1 by a dippingmethod at a lifting speed of 3 mm/sec under a relative humidity of 50%.Then, the glass substrate was dried in the air for 30 minutes andsubsequently heat-treated at 300° C. for 1 hour. The above procedure wasrepeated to conduct the coating twice to give a glass substrate providedwith an amorphous aluminum oxide layer. The obtained glass substrate wastreated with hot water to form a fine texture of boehmite on aluminumoxide. The glass substrate was put in a stainless steel holder and wasimmersed in pure water at 80° C. for 30 minutes and then dried at 100°C. The glass substrate was immersed in the phosphoric acid compoundtreatment solution 1 of Example 1 and then lifted at a speed of 3mm/sec. The glass substrate was heated at 60° C. for 1 hour to giveglass 7.

The glass 7 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%). It was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 99.5%, and the haze value measured with a hazemeter was 0.11.

Example 8

An optical glass containing 30 wt % of B₂O₃ and having a refractiveindex of 1.77 was used as the base material.

The TiO₂ sol solution was added to the SiO₂ sol solution of Example 7 ata molar ratio of SiO₂:TiO₂=80:20. The resulting mixture was stirred atroom temperature for 2 hours to give a coating solution for a SiO₂—TiO₂intermediate film. A coating film was formed using this coating solutionfor an intermediate film on a surface of the glass substrate by adipping method at a lifting speed of 2 mm/sec under a relative humidityof 60%. After drying at room temperature, the glass substrate was heatedat 300° C. for 1 hour to give a glass substrate provided with atransparent amorphous SiO₂—TiO₂ film.

The glass substrate provided with the intermediate film was coated withan amorphous aluminum oxide coating solution of Example 1 by a dippingmethod at a lifting speed of 3 mm/sec under a relative humidity of 50%.Then, the glass substrate was dried in the air for 30 minutes andsubsequently heated-treated at 300° C. for 1 hour. The above procedurewas repeated to conduct the coating twice to give a glass substrateprovided with an amorphous aluminum oxide layer. The obtained glasssubstrate was treated with hot water to form a fine texture of aluminumoxide. The glass substrate was put in a stainless steel holder and wasimmersed in pure water at 80° C. for 30 minutes and then dried at 100°C. The glass substrate was immersed in the phosphoric acid compoundtreatment solution 1 and then lifted at a speed of 3 mm/sec. The glasssubstrate was heated at 60° C. for 1 hour to give glass 8.

The glass 8 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%). It was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 99.4%, and the haze value measured with a hazemeter was 0.09.

Example 9

An optical glass containing 7 wt % of Na₂O and having a refractive indexof 1.65 was used as the base material.

The TiO₂ sol solution was added to the SiO₂ sol solution of Example 7 ata molar ratio of SiO₂:TiO₂=80:20. The resulting mixture was stirred atroom temperature for 2 hours to give a coating solution for a SiO₂—TiO₂intermediate film. A coating film was formed on a surface of the glasssubstrate using this coating solution for an intermediate film by adipping method at a lifting speed of 1.5 mm/sec under a relativehumidity of 60%. After drying at room temperature, the glass substratewas heated at 300° C. for 1 hour to give a glass substrate provided witha transparent amorphous SiO₂—TiO₂ film.

The glass substrate provided with the intermediate film was coated withan amorphous aluminum oxide coating solution of Example 1 by a dippingmethod at a lifting speed of 3 mm/sec under a relative humidity of 50%.Then, the glass substrate was dried in the air for 30 minutes andsubsequently heat-treated at 300° C. for 1 hour. The above procedure wasrepeated to conduct the coating twice to give a glass substrate providedwith an amorphous aluminum oxide layer. The obtained glass substrate wastreated with hot water to form a fine texture of aluminum oxide. Theglass substrate was put in a stainless steel holder and was immersed inpure water at 80° C. for 30 minutes and then dried at 100° C. The glasssubstrate was immersed in the phosphoric acid compound treatmentsolution 1 and then lifted at a speed of 3 mm/sec. The glass substratewas heated at 60° C. for 1 hour to give glass 9.

The glass 9 was subjected to a durability test under the above-mentioneddurability test conditions (a temperature of 60° C., a relative humidityof 90%). It was confirmed that no change in the appearance occurredduring the durability test. The transmittance measured with aspectrophotometer was 99.6%, and the haze value measured with a hazemeter was 0.10.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

This application claims the benefit of Japanese Application No.2007-011429 filed Jan. 22, 2007 and No. 2008-002164 filed Jan. 9, 2008,which are hereby incorporated by reference herein in their entirety.

1. An optical member comprising: a base material; and an antireflectioncoating on a surface of the base material, wherein the antireflectioncoating includes at least an oxide layer having a fine texturedstructure on the surface and containing phosphorus.
 2. The opticalmember according to claim 1, wherein the oxide layer includes anamorphous layer and the fine textured structure formed of anisotropiccrystalline particles.
 3. The optical member according to claim 2,wherein the fine textured structure has a shape that can sequentiallydecrease refractive indices from the boundary with the amorphous layertoward the surface of the oxide layer.
 4. The optical member accordingto claim 1, wherein the fine textured structure has a height of 0.1 μmor more and 5 μm or less.
 5. The optical member according to claim 2,wherein the anisotropic crystalline particles are plate-like.
 6. Theoptical member according to claim 5, wherein the plate-like particlesare boehmite particles.
 7. The optical member according to claim 1,wherein the base material is a transparent glass containing an elementselected from the group consisting of an alkali, an alkaline earth, andboron.
 8. A method of manufacturing an optical member having a basematerial and an oxide layer, the method comprising: forming an oxidelayer provided with a fine textured structure thereon on a surface of abase material; and phosphating the oxide layer provided with the finetextured structure thereon.
 9. The method of manufacturing an opticalmember according to claim 8, wherein the water-soluble phosphoric acidcompound contains metal dihydrogen phosphate or amine phosphate as amain component.
 10. The method of manufacturing an optical memberaccording to claim 8, wherein the water-soluble phosphoric acid compoundis present in the form of an aqueous dispersion; and the content of thephosphoric acid compound in the dispersion is 0.01% by weight or moreand 30% by weight or less.
 11. The method of manufacturing an opticalmember according to claim 8, wherein the forming of the fine texturedstructure on the surface of the oxide layer is conducted by forminganisotropic particles of an oxide by bringing a film containing a metalinto contact with water.
 12. The method of manufacturing an opticalmember according to claim 11, wherein the metal is aluminum; and theanisotropic particles of an oxide is boehmite.
 13. The optical memberaccording to claim 1, wherein the oxide layer containing a phosphatecompound.